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191 lines
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191 lines
5.8 KiB
Markdown
page_title: Dockerizing a Node.js Web App
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page_description: Installing and running a Node.js app with Docker
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page_keywords: docker, example, package installation, node, centos
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# Dockerizing a Node.js Web App
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> **Note**:
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> - **If you don't like sudo** then see [*Giving non-root
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> access*](/installation/binaries/#giving-non-root-access)
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The goal of this example is to show you how you can build your own
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Docker images from a parent image using a `Dockerfile`
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. We will do that by making a simple Node.js hello world web
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application running on CentOS. You can get the full source code at
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[https://github.com/enokd/docker-node-hello/](https://github.com/enokd/docker-node-hello/).
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## Create Node.js app
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First, create a directory `src` where all the files
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would live. Then create a `package.json` file that
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describes your app and its dependencies:
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{
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"name": "docker-centos-hello",
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"private": true,
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"version": "0.0.1",
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"description": "Node.js Hello world app on CentOS using docker",
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"author": "Daniel Gasienica <daniel@gasienica.ch>",
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"dependencies": {
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"express": "3.2.4"
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}
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}
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Then, create an `index.js` file that defines a web
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app using the [Express.js](http://expressjs.com/) framework:
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var express = require('express');
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// Constants
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var PORT = 8080;
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// App
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var app = express();
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app.get('/', function (req, res) {
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res.send('Hello world\n');
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});
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app.listen(PORT);
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console.log('Running on http://localhost:' + PORT);
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In the next steps, we'll look at how you can run this app inside a
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CentOS container using Docker. First, you'll need to build a Docker
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image of your app.
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## Creating a Dockerfile
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Create an empty file called `Dockerfile`:
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touch Dockerfile
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Open the `Dockerfile` in your favorite text editor
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Define the parent image you want to use to build your own image on
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top of. Here, we'll use
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[CentOS](https://registry.hub.docker.com/_/centos/) (tag: `centos6`)
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available on the [Docker Hub](https://hub.docker.com/):
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FROM centos:centos6
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Since we're building a Node.js app, you'll have to install Node.js as
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well as npm on your CentOS image. Node.js is required to run your app
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and npm to install your app's dependencies defined in
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`package.json`. To install the right package for
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CentOS, we'll use the instructions from the [Node.js wiki](
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https://github.com/joyent/node/wiki/Installing-Node.js-
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via-package-manager#rhelcentosscientific-linux-6):
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# Enable EPEL for Node.js
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RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
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# Install Node.js and npm
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RUN yum install -y npm
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To bundle your app's source code inside the Docker image, use the `COPY`
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instruction:
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# Bundle app source
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COPY . /src
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Install your app dependencies using the `npm` binary:
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# Install app dependencies
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RUN cd /src; npm install
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Your app binds to port `8080` so you'll use the` EXPOSE` instruction to have
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it mapped by the `docker` daemon:
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EXPOSE 8080
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Last but not least, define the command to run your app using `CMD` which
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defines your runtime, i.e. `node`, and the path to our app, i.e. `src/index.js`
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(see the step where we added the source to the container):
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CMD ["node", "/src/index.js"]
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Your `Dockerfile` should now look like this:
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FROM centos:centos6
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# Enable EPEL for Node.js
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RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
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# Install Node.js and npm
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RUN yum install -y npm
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# Bundle app source
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COPY . /src
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# Install app dependencies
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RUN cd /src; npm install
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EXPOSE 8080
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CMD ["node", "/src/index.js"]
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## Building your image
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Go to the directory that has your `Dockerfile` and run the following command
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to build a Docker image. The `-t` flag lets you tag your image so it's easier
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to find later using the `docker images` command:
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$ sudo docker build -t <your username>/centos-node-hello .
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Your image will now be listed by Docker:
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$ sudo docker images
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# Example
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REPOSITORY TAG ID CREATED
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centos centos6 539c0211cd76 8 weeks ago
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<your username>/centos-node-hello latest d64d3505b0d2 2 hours ago
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## Run the image
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Running your image with `-d` runs the container in detached mode, leaving the
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container running in the background. The `-p` flag redirects a public port to
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a private port in the container. Run the image you previously built:
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$ sudo docker run -p 49160:8080 -d <your username>/centos-node-hello
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Print the output of your app:
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# Get container ID
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$ sudo docker ps
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# Print app output
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$ sudo docker logs <container id>
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# Example
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Running on http://localhost:8080
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## Test
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To test your app, get the the port of your app that Docker mapped:
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$ sudo docker ps
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# Example
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ID IMAGE COMMAND ... PORTS
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ecce33b30ebf <your username>/centos-node-hello:latest node /src/index.js 49160->8080
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In the example above, Docker mapped the `8080` port of the container to `49160`.
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Now you can call your app using `curl` (install if needed via:
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`sudo apt-get install curl`):
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$ curl -i localhost:49160
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HTTP/1.1 200 OK
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X-Powered-By: Express
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Content-Type: text/html; charset=utf-8
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Content-Length: 12
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Date: Sun, 02 Jun 2013 03:53:22 GMT
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Connection: keep-alive
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Hello world
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If you use Boot2docker on OS X, the port is actually mapped to the Docker host VM,
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and you should use the following command:
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$ curl $(boot2docker ip):49160
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We hope this tutorial helped you get up and running with Node.js and
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CentOS on Docker. You can get the full source code at
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[https://github.com/enokd/docker-node-hello/](https://github.com/enokd/docker-node-hello/).
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